The present invention relates to a method and apparatus for exchanging full roving bobbins, which are held ready on a ring spinning machine, for empty or nearly empty roving bobbins on the ring spinning machine. More specifically the present invention relates to a method and apparatus for automatically exchanging roving bobbins with the aid of a traveling service unit movable to the stations of the ring spinning machine.
When a roving bobbin which feeds yarn to a ring spinning machine is empty, the bobbin must be exchanged for the spinning process to continue. It is possible to allow the yarn from the roving bobbin to fully run out before exchanging the bobbin for a full roving bobbin; however, the yarn from the new roving bobbin must then be fed into the ring spinning machine before the spinning process can continue. Preferably the roving bobbin is exchanged before it is completely unwound, for it is then possible to piece the roving from the full roving bobbin with the roving from the nearly empty bobbin so that the spinning process can continue uninterrupted.
In European published Patent Application No. 0 213 962, a method and an apparatus for simultaneously exchanging full and empty roving bobbins is described and includes two sets of gripping elements. One set of gripping elements removes the full roving bobbin from the spare bobbin frame and holds it while the other set of gripping elements removes the empty bobbin from the roving bobbin holder. The two sets of gripping elements then operate simultaneously to move the empty bobbin onto the spare bobbin frame and the full bobbins to the bobbin holder. However, as this method requires that the gripping elements be simultaneously moved past each other, complex movement paths are inherent, adding to the equipment and production costs of the spinning process. Moreover, this known method and apparatus is only adapted to service the outermost row of bobbins on the roving bobbin holder so that the inner row of empty bobbins must be brought outward to the outer row position in order to then be exchanged for full bobbins. This requirement to position the bobbins to be exchanged in the outermost row adds as well to the equipment and production costs.
In German Patent A-24 38 247, a roving bobbin exchange apparatus is described and includes two similarly outfitted service units which sequentially service the spinning stations. The gripping element of one service unit takes the full roving bobbins from the spare bobbin frame and holds them ready while the other service unit removes the empty bobbins. In German Patent B-21 58 657, a method for exchanging full roving bobbins for empty bobbins is described and includes a so-called block exchange in which all of the bobbins of one side of a machine are simultaneously exchanged. However, this method requires the use of apparatus built onto the ring spinning machine itself for initially moving the empty bobbins to an intermediate position during the time that the full bobbins are loaded onto the roving bobbin holder and this limits the adaptability of this method.
Accordingly, the need exists for a method and apparatus for simply and reliably exchanging empty bobbins on a ring spinning machine for full bobbins with little or no disruption of the spinning process.